Bulk eraser with permanent magnet flux produced obliquely to cassette movement

ABSTRACT

A bulk eraser for a recorded magnetic medium, the eraser consisting of a housing having a passage for the recorded magnetic medium and magnet means arranged adjacent said passage.

United States Patent Ohira et al.

1451 May 2, 1972 154] BULK ERASER WITH PERMANENT MAGNET FLUX PRODUCEDOBLIQUELY TO CASSETTE MOVEMENT [72] inventors: Shigemasa Ohlra,Kanagawa-ken; Hlsoshi Hanzawa; Hisaya Narita, both of Tokyo,

all of Japan [73] Assignee: Sony Corporation, Tokyo, Japan [22] Filed:Oct. 9, 1969 [21 Appl. No.: 870,482

[30] Foreign Application Priority Data Oct. 16, 1968 Japan ..43/75398Oct. 16, 1968 Japan ....43/90l95 Oct. 16, 1968 Japan ..43/90196 [52]U.S. Cl. ..317/157.5, 179/100.2 D [51] Int. Cl. ..H0li13/00 [58] FieldoiSearch ..179/100.2 D;317/157.5, 157.51

[56] References Cited UNITED STATES PATENTS 2,481,392 9/1949 Camras..317/157.5 R 3,023,280 2/1962 Tronslin et a1. 1 79/1002 D 3,143,6898/1964 Hall ..179/100.2 D 3,506,884 4/1970 McKinley ..317/157.S R

Primary ExaminerBernard Konick Assistant Examiner-Alfred H. EddlcmzmAttorney-Curtis, Morris & Safford [57] ABSTRACT A bulk eraser for arecorded magnetic medium, the eraser consisting of a housing having apassage for the recorded magnetic medium and magnet means arrangedadjacent said passage.

7 Claims, 10 Drawing Figures Patehted May 2, 1972 -3,660,727

6 Shoots-Shoot 1 INVIL'N'I'OR.

SHIGEMASA OHIRA HISAYA NARITA HISASHI HANZAWA BY A'I'TURN/i Y6 PatentedMay 2, 1 972 7 6 Sheets-Sheet 2 INVENTOR- mm A .AZ NN A MH A m 5 A .6. HA 1 H O A S A M E m H S 6 Sheets- Sheet 5 I N VEN'I UR.

SHIGEMASA OHIRA HISAYA NARITA HISASHI HANZAWA Patented May 2, 1972 6Sheets-Sheet 5 SHGEMASA OHIRA HISAYA NKFVQIEN'IFX HISASHI HANZAWAPatented May 2, 1972 6 Sheets-Sheet 6 SHIGEMAVSAV OHIRA IN VliN'I OR.

HISAYA NARI TA' HI SA SHI HANZAWA BULK ERASER WITH PERMANENT MAGNET FLUXPRODUCED OBLIQUELY TO CASSETTE MOVEMENT BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to a bulk eraser, and moreparticularly to a bulk eraser which is of small size and is easy tohandie.

2. Description of the Prior Art A conventional bulk eraser consists ofan E-shaped iron core having a coil wound thereon. A magnetic medium isplaced on the core and then an attenuating alternating current isapplied to the coil to erase the information recorded on the magneticmedium. It is also possible to serve the same purpose by graduallydrawing the magnetic medium and the core apart without attenuating thecurrent applied to the coil. However, the former method requires meansfor producing the attenuating alternating current and the latternecessitates means for drawing the magnetic medium and the core apart.Consequently, the conventional bulk eraser becomes bulky and expensive.In addition, the use of the alternating current imposes a limitation onthe place of actual use of the bulk eraser and introduces complexity inits handling. A bulk eraser using a permanent magnet is easy to handlebut cannot be expected to achieve satisfactory erasing.

SUMMARY OF THE INVENTION The present invention is directed to a bulkeraser which is provided with a housing having a passage permitting aspirally wound magnetic medium to pass therethrough and having magnetmeans disposed adjacent the passage to produce a magnetic flux obliquelyto the direction in which the magnetic medium is moved.

Accordingly, one object of the invention is to provide a small-sized andinexpensive bulk eraser.

Another object of this invention is to provide a bulk eraser whichensures erasure of recorded contents with simple operatlons.

A further object of this invention is to provide a bulk eraser which isprovided with means for prevent the eraser by mistake of recordedcontents that it is desired to preserve.

Still a further object of this invention is to provide a bulk eraserwhich is adapted to keep the magnet means clean at all times.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows in perspective a deviceof this invention in its inoperative condition;

FIGS. 2 and 3 illustrate in perspective the device of this invention inits operative condition;

FIGS. 4 and 5 are top plan and side views partly in crosssection,showing the device of this invention;

FIG. 6 is a cross-sectional view of the principal part of a cover of thedevice in FIG. 5;

FIG. 7 is a perspective view of means used in the present invention toprevent undesired erasure of record material;

FIG. 8 shows in perspective a cassette having incorporated therein amagnetic tape;

FIG. 9 schematically shows the magnetic tape wound on a reel; and

FIG. 10 is a perspective view of reel locking means used in the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings referencenumeral 1 indicates a housing having a passage 2 through which aspirally wound magnetic medium M can be passed. The housing 1 has inletand outlet openings 3 and 4 at opposite ends of the passage 2. Thehousing 1 has side walls 5 and 6, on the inside of which are disposedpermanent magnets 7 and 8 adjacent the passage 2. In this case thepermanent magnets 7 and 8 are disposed in a predetermined spacedrelation to each other relative to the direction of movement of theconvoluted magnetic medium M, as depicted in FIGS. 4 and 5. The magnets7 and 8 are magnetized in a direction parallel to their thickness and insuch a manner that their proximal inner surfaces on the side of thepassage 2 consist entirely of the south and north magnetic poles, orvice versa. Adjacent magnets 7 and 8 are magnetized with oppositemagnetic poles. Further, adjacent magnets 7 and 8 are disposed so that aplane B defined by their opposing edges 70 and 8a is inclined at anangle of, for example, 45 degrees to the direction in which the magneticmedium M is pushed into the passage 2 as indicated by an arrow A.Consequently, magnetic lines of force through the plane B are indicatedby an arrow C and are inclined at an angle of, for example, 135 degreesto the direction of the arrow A. The magnets 7 and 8 are fixedly mountedon the inside of the side walls 5 and 6 of the housing 1 through plasticframes 9, which may be formed by molding.

Reference numeral 10 indicates a front wall or cover which is hingedabout a pin 11 and serves as a closure for one opening of the passage 2.The cover 10 has a guide portion 12 which leads to the passage 2 whenheld horizontal while the bulk eraser is in actual use as illustrated inFIG. 5. Further, the cover 10 has a member 13 for preventing undesirederasure of the information recorded on a magnetic medium which it isdesired to preserve. The member 13 that is to prevent incorrect erasureretains the magnetic medium M on the cover 10 to prevent it from movinginto the passage 2. This member cooperates with erasure-prevention meanson a cassette, as described later.

As shown in FIGS. 6 and 7, the means for prevention of undesired, andtherefore faulty, erasure includes a member 13 that consists of adetector member 14 and a member 15, which shifts with a displacement ofthe detector member 14 to obstruct the movement of the magnetic mediumM. The detector means 14 comprises upstanding lugs 16 and 17 and a platespring 19 that urges the lugs upwardly. The plate spring 19 is fixed atits center to the interior wall 10a of the cover 10 and the lugs 16 and17 project out through openings 20 and 21 bored through the guideportion 12 of the cover 10. The distance between the lugs 16 and 17 isselected to be the same as that between the faulty erasure preventionmembers of the cassette described later. Reference numerals 22 and 23designate notches formed in the detector member 14.

The member 15 consists of a slide lever 45, extension arms 24 and 25bent from the slide lever 45 and engaging the notches 22 and 23, and astopper 27 rotatably hinged about a pin 26 at one end of the slide lever45. The extension arms 24 and 25 are held flush with the notches 22 and23. The slide lever 45 is guided in a horizontal direction by an opening28 and a bar 29. Reference numeral 30 designates a coil spring whichalways pulls the slide lever 45 to the right.

In FIGS. 3 and 4 two covers 31 and 32 for the other opening 4 of thepassage 2 are hinged about pins 33 and 34 and open together on theirrespective hinges. The covers 31 and 32 are made of, for example, amagnetic material and are normally attracted by the magnets 7 and 8 toclose the opening 4. Further, one end face of each of the frames 9serves as a stopper for each of the covers 31 and 32 to preventinsertion of the magnetic medium M via the opening 4.

Turning now to FIG. 8, a description will be given of a cassette 35. Thecassette 35 has a case 38 within which is a magnetic medium M wound onreels 36 and 37, as shown in FIG. 9. The case 38 has formed in its rearface members 39 and 40 in the forms of thin tabs 39a and 40a thatcontrol erasure of the magnetic medium. Ifthe tabs 39a and 40a arepresent new information can be recorded on the magnetic medium. However,if the recorded material is not to be erased the tabs are snapped off.Thereafter, recording cannot be made on the magnetic medium, thusensuring no inadvertent erasure of the information content recorded onthe magnetic medium. Such a cassette is well-known as a compact cassettemanufactured by N. V. Philips Gloeilampenfabrieken.

In FIG. reference numeral 41 designates, generally, reel lock consistingof a plate 42 formed of, for example, synthetic resin and lock members43 and 44, which are formed integrally with the plate 42 and engagereels 36 and 37 of the cassette 35 to prevent their rotation. Each ofthe lock members 43 and 44 has, for example, three projecting pieces,which engage inwardly projecting teeth of the reel hub. In thedemagnetization of the magnetic medium M housed in the cassette 35, thereel lock 41 is mounted on the cassette 35 in such a manner that thelock members 43 and 44 are held in engagement with the reels 36 and 37,under which conditions the cassette 35 is passed through the passage 2.

A description will be given of the operation of the bulk eraser of sucha construction as has been described in the foregoing.

The cover 10 is opened at an angle of 90 degrees and the cassette 35 isplaced on the guide portion 12 of the cover 10 as shown in FIGS. 2 and5, under which conditions the cassette 35 is pushed in the direction ofthe arrow A. In such a case the domains of the magnetic materials onthose portions Ma of the magnetic medium M which are substantiallyparallel with the magnetic lines of force indicated by C are all alignedin the direction C, so that the portions Ma are demagnetized. Then, thecassette 35 is turned over and passed through the passage 2, in whichcase the portions Mb of the magnetic medium M are substantially parallelwith the magnetic lines of force and are thereby demagnetized in asimilar manner. Thus, the magnetic medium M can be readily demagnetizedwhile being wound on the reel 36.

In some cases, when the cassette 35 passes between the opposing magnets7 and 8, the magnetic medium M wound on the reels 36 and 37 is turned bythe magnetic lines of force of the magnets 7 and 8. Consequently,although the cassette 35 is passed twice through the bulk eraser, it islikely that some portions of the magnetic medium M will be leftmagnetized by the turning of the magnetic medium itself. To avoid this,the lock members 43 and 44 of the reel lock 41 depicted in FIG. 10 areengaged with the reels 36 and 37 as illustrated in FIG. 2.

Referring now to FIGS. 6 and 7, the operation of the faultyerasuremember 13 will be described. In the demagnetization of the magneticmedium M, when the tabs 39a and 40a of the cassette 35 are present, thelugs 16 and 17 are both pushed by the tabs 39a and 40a in a direction ofthe arrow D. Consequently, the extension arms 24 and 25 of the slidelever 45 are not flush with the notches 22 and 23 of the detector member14, as would be required to allow the slide lever 45 to moveindependently of the detector member 14. Pressing the stopper 27 withthe side 35a of cassette 35 to the left causes the stopper 27 to bemoved to the left, together with the slide lever 45, and to be turned ina counterclockwise direction, thereby to guide the cassette 35 to thepassage 2. In this case the reel lock 41 is mounted on the cassette 35as above described. In the event that only one tab 39a of the cassette35 has been removed, the lug 17 is pressed down by the tab 400 but theother lug 16 is pushed upward by the plate spring 19. Accordingly, theextension arm 25 is not flush with the notch 23, but the arm 24 liesflush with the notch 22 and engages therewith, so that the slide lever45 is prevented from moving to the left, and the stopper 17 does notturn, thus retaining the cassette 35 on the cover 10 and eliminating thepossibility of inadvertent erasure of the information content recordedon the magnetic medium M. It will be seen that where both tabs 39a and40a have been removed, the movement of the slide lever 45 is alsoprevented, thereby retaining the cassette on the cover 10. The manner inwhich the cassette 35 moves from the passage 2 is shown in FIG. 3. Thecassette 35 pushes open the covers 31 and 32, and when the cassette 35has been completely removed from the passage 2, the covers 31 and 32 areattracted by the magnetic force of the magnets 7 and 8 to close theopening of the passage 2 to keep the magnets 7 and 8 clean.

As has been described in the foregoing, the present invention enablesnot only demagnetization of a magnetic medium wound on a reel but alsoprevents faulty erasure of the |nformation content recorded on themagnetic medium. Further, the present invention does not require a powersource, so that the bulk eraser of this invention can be used as aportable eraser for magnetic tapes incorporated in cassettes. It issimple in construction. While two permanent magnets of oppositepolarities are arranged in the foregoing embodiment, the same resultscan be obtained by sequentially arranging more than three permanentmagnets in an order ofS, N, S, N, or N, S, N, S In this case, if thedemagnetizing portion is formed such that the opposing planes of thenorth and south magnetic poles of the first and second magnets and thoseof the south and north magnetic poles of the second and third magnetsare inclined at different angles, one passage of a magnetic mediumthrough the eraser will be sufficient for its demagnetization. In theforegoing example the permanent magnets are mounted on both inside wallsof the housing but it will be understood that the demagnetization effectsimilar to the aforementioned can be obtained by disposing the permanentmagnets on one inside wall of the housing as above described.

Although the opposing plane B between the magnets 7 and 8 is inclined at45 degrees to the direction A, it may be inclined at any other angle.Further,it will be seen that the above effects can be obtained with notonly the Philips type cassette tape but also a magnetic tape wound on astandard reel, if a case for supporting the tape is provided as anadapter and faulty-erasure prevention are provided in the case.

It will be apparent that many modifications and variations may beefi'ected without departing from the scope of the novel concepts of thisinvention.

We claim:

1. A bulk eraser for a tape cassette comprising a case, two reels, andtape wound thereon, said eraser comprising:

A. A housing having juxtaposed walls defining a passage through which atape cassette can be passed;

B. Permanent magnet means on said walls facing said passage and havingpoles producing magnetic flux obliquely to the direction of movement ofthe tape cassette through passage;

C. A cover pivotally mounted on said housing at one end of said passageand normally biased into position to close said passage; and

D. Guide means comprising a Hat portion to receive said tape cassette,said guide portion being pivotally mounted on said housing to keep theother end of said passage normally closed, said flat portion guidingsaid tape cassette into said passage when said guide means is pivotedoutwardly.

2. A bulk eraser as claimed in claim 1 comprising means engaging saidcassette for preventing, erasure of information intended to bepennanently recorded on the tape.

3. A bulk eraser as claimed in claim 1 wherein the guide means includesmeans for detecting the means for preventing faulty erasure and meansfor preventing the movement of the tape in cooperation with thedetecting means.

4. A bulk eraser as claimed in claim 1 which includes means for lockingthe reels in said cassette with the tape wound thereon.

5. A bulk eraser as claimed in claim 1 which has covers for closing theother open end of the passage.

6. A bulk eraser as claimed in claim 5 wherein the covers include meanswhich permits the opening of the covers from the inside by the magneticmedium having passed the passage but prevents the insertion of themagnetic medium from the outside.

7. A bulk eraser as claimed in claim 5 wherein the covers are attractedby the magnetic force of the magnet means to close the passage.

1. A bulk eraser for a tape cassette comprising a case, two reels, andtape wound thereon, said eraser comprising: A. A housing havingjuxtaposed walls defining a passage through which a tape cassette can bepassed; B. Permanent magnet means on said walls facing said passage andhaving poles producing magnetic flux obliquely to the direction ofmovement of the tape cassette through passage; C. A cover pivotallymounted on said housing at one end of said passage and normally biasedinto position to close said passage; and D. Guide means comprising aflat portion to receive said tape cassette, said guide portion beingpivotally mounted on said housing to keep the other end of said passagenormally closed, said flat portion guiding said tape cassette into saidpassage when said guide means is pivoted outwardly.
 2. A bulk eraser asclaimed in claim 1 comprising means engaging said cassette forpreventing, erasure of information intended to be permanently recordedon the tape.
 3. A bulk eraser as claimed in claim 1 wherein the guidemeans includes means for detecting the means for preventing faultyerasure and means for preventing the movement of the tape in cooperationwith the detecting means.
 4. A bulk eraser as claimed in claim 1 whichincludes means for locking the reels in said cassette with the tapewound thereon.
 5. A bulk eraser as claimed in claim 1 which has coversfor closing the other open end of the passage.
 6. A bulk eraser asclaimed in claim 5 wherein the covers include means which permits theopening of the covers from the inside by the magnetic medium havingpassed the passage but prevents the insertion of the magnetic mediumfrom the outside.
 7. A bulk eraser as claimed in claim 5 wherein thecovers are attracted by the magnetic force of the magnet means to closethe passage.